Policy control is a process for controlling the use of network resources according to a predefined policy. The policy typically comprises a formal set of rules that govern how network resources may be used. When a mobile device attempts to access a network or invoke a service, the policy control function determines whether the access or service is allowed based on the policy established by the service provider. Policy rules may be enforced through admission control and/or quality of service (QoS) control.
In IP Multimedia Subsystem (IMS) networks, the policy control function is implemented by two functional entities: The policy enforcement point and the policy decision point. the policy enforcement point typically resides in a node through which user traffic flows. The policy enforcement point blocks or permits user traffic based on the applicable policies. The policy decision point is a policy server that determines what policy rules apply to a given service. A network typically comprises a plurality of policy decision points or policy servers that are allocated to serve particular mobile devices.
The demands for capacity in policy servers in emerging networks are likely to grow for several reasons. The current static nature of policies means that the policy decision point, or policy server, is typically involved only during service and bearer establishment. When more advanced and dynamic policies are introduced, the policy servers will have to continuously collect dynamic input data for making policy decisions. Additionally, the growing number of subscribers and the adoption rate of packet data services indicate that the load on policy servers will increase.
Given the increasing demands on policy servers, an efficient, flexible, and easily-scalable policy control architecture is needed to meet the increased demand on policy server resources.